It is a characteristic of those unable to rationally argue a point, either scientifically or conceptually, to change the argument to a different point designed to elicit an emotional response.
Plant and crop growth is not the issue with this graph, rather the intentional manipulation of data. Anyone doing this on a doctoral dissertation, for example, would be dismissed for academic fraud.
As for your intended change of topic, crop growth has a considerable number of factors involved, inclusive but not exclusive to yearly mean temperatures. Moreover, this graph relates issues specific to tampering with data from Michigan, which is not among the largest agricultural producing states in the Union, thereby invalidating the attempt to relate this to more widespread issues of starvation.
Most issues of starvation more relate to the ability to transport food rather than produce it (please see some rather interesting left-leaning works by Jared Diamond including “Guns, Germs, and Steel”). If this were not the case, we would not be spending as much in farm subsidies to attempt to keep farms from overproducing and depressing the market.
Please keep your emotional, scientific myopia in check.

By far the worst crop failures in US history took place during the 1930’s. That is approximately 80 years ago, long before manmade CO2 was considered to be an important factor.

Those crop failures also coincided with by far the hottest temperatures ever recorded in most parts of the US. For example, Saginaw in northern lower Michigan, where a 100 degree day is rare, had a week in 1936 where the average high temperature was 106.5 and the hottest day reached 112.

The US was importing grain in 1936! So plants have actually been doing relatively quite well during recent years.

The U.S. was importing grain in the 1930s due to the catastrophic failure of FDR’s Agricultural Adjustment Act, which used tax dollars to pay American farmers to destroy crops and livestock, much as Herbert Hoover’s Federal Farm Board did before it. American farmers were paid to take farmland out of production and crop prices were kept artificially high via federal price fixing and subsidies. The result was that for the first time ever, the U.S. had to become a food-importing nation to feed its own people. From 1934 to 1935, the U.S. more than quadrupled the amount of wheat it imported, all while making prices higher during an extreme economic downturn as millions of Americans were already struggling to provide their children’s next meal. This was the era when, regrettably, big-scale government interference in agriculture became institutionalized. The Department of Agriculture became one of the largest and most powerful federal entities. More liberal-socialist-progressive meddling in the economy and people’s lives, all to disastrous effect. See Frank Kent, Without Grease: Political Behavior, 1934-1936, p. 250.